Which difficulty will give the closest to the intended experience. I don't care if it's too hard or easy; I want the "true" experience. Thoughts?

I would assume normal difficulty? Harder difficulties tend to add multiplies to how hard monsters hit you for and reduce the amount of damage you do. So for example normal difficulty is probably x1 to how much damage player deals and x1 to how much damage monsters deal whereas hard difficulty could be something like x0.5 player damage and x1.5 monster damage.

That's what I would think too, but sometimes it can be weird. Like how in Dragon Age: Origins the best difficulty was Nightmare and everything was scaled down, but in Dragon Age 2, it was balanced around Normal like you said. Or in Mass Effect 1 & 2, Hardcore usually puts you on equal footing with the enemy while Insanity makes them better than you (which I found weird as a Spectre being outclassed by a random merc). So while I usually expect Normal to be standard and then scaled, there are some exceptions.

Well i'm playing on the hardest difficulty cause that's usually how I always play and monsters are basically HP sponges with the crappy gear you start off with as well as being easily one shot killed although I imagine that problem goes away as you get better gear and such. But yeah unless we get someone going into the the files or the code and telling us exactly what difficulty modifies then we can't know for certain where it stands.

Monsters are damage-sponges even on Normal.

I think any difficult is legit for this.